typically the three beeps is followed by an alert message on the info centre display on the centre dash that says "Motor Control Systems Failure" and usually tells you something like go to dealer.
this should also generate an orange engine shaped warning light on the dash to show an error code has been generated.
thats all it means is there is a fault code, it can be something simple or it can be a major fault.
I have had phantom errors before now where it will flash up for a second, usually on startup and then disappear immediately and have not really ever thought anything of it.
1999 156 1.8TS Sport Pack 3
2001 166 3.0 V6 24V Super
2003 156 GTA 3.2 V6 24V
2005 156 1.9 JTDM-Jet Sport
2008 159 1.9 JTDM Lusso
1997 GTV 2.0TS Lusso
2001 147 1.6TS Lusso